1. Field of the Invention
The present invention relates to a flat motor device, method and apparatus for producing the same, in which flat motor device, a fan is rotated by a flat motor (for example, such as a print motor, wire-wound type flat motor, etc.).
2. Description of the Prior Art
In flat motor devices used for blower devices of a radiator cooling apparatus for automobiles or an air conditioning apparatus for automobiles, a fan is mounted at the end of a shaft projected from the motor (see, for example, such as Japanese Patent Application Laid-Open No. 2,841/1987, Japanese Utility Model Application Laid-Open No. 199,152/1986, Japanese Patent Application Laid-Open No. 18,014/1972, and Japanese Patent Application Laid-Open No. 32,099/1982).
In the motor used for such a flat motor device, a closed casing is formed by a first bracket and a second bracket, which are formed from a plate-like flat plate, a shaft is rotatably supported within the closed casing, and a rotor hub is mounted on the shaft through a sleeve. The rotor hub, which is made of synthetic resin, has a rotor portion mounted thereon which has a commutator and an armature electrically connected to the commutator.
A feeder brush comes into contact with the commutator, and a turning force is produced by interaction between a magnetic force provided through a slight clearance relative to the armature and an electric current flowing into the armature.
On the other hand, a flat portion cut off by a milling machine or the like is formed on the end of the aforesaid shaft, a fan having a center hole having the same shape as that of said flat portion and a fan plate are fitted into said flat portion, a nut is screwed into the threads formed on the end of said shaft, and said fan and said fan plate are held between a shoulder created by forming said flat portion and the nut.
In the case where such a flat motor device is produced, there are employed (A) a method in which a shaft is directly pressed into a center hole of the rotor rub (see the aforesaid Japanese Patent Application Laid-Open No. 18,014/1962) (B) a method in which a sleeve is inserted through the center of the rotor rub, and a shaft is inserted into the sleeve (see the aforesaid Japanese Patent Application Laid-Open No. 2,841/1987).
If a flat motor device is produced without using such a sleeve as described in the former reference, the following inconveniences occur.
First, if the rotor hub is directly resin-molded on the shaft without using a sleeve, when a male die and a female die are not closely coincided at the time of resin molding, corners or the like of the die touches on the surface of a shaft finished with high precision during spotting, possibly damaging the surface of the shaft.
Secondly, during the resin molding, the resin flows along the surface of the shaft from a clearance between the dies, possibly making the resin adhere to unnecessary portions.
Thirdly, during pressing, there possibly effects cracks in a rotor hub made of resin.
However, in the case of the rotor portion having a sleeve provided between a shaft and a rotor hub as described in the later reference, the shaft need to be formed with a knurling portion having the outside diameter larger than the inside diameter of the sleeve so as to provide a positive engagement between the sleeve and the shaft. With this arrangement, the sleeve is, when pressed in, inflated radially outwardly by the knurling porton, and the rotor hub made of resin in the outer periphery of the sleeve possibly cracks due to the inflation.
In order to prevent the occurrence of such a crack, a proposal has been made so that the engaging portion between the sleeve and the knurling portion is made axially and externally of the rotor hub. However, this increases an axial dimension of the flat motor device to materially impair the effectual properties of the flat motor.
Moreover, use of such a sleeve brings forth an increase in number of parts, being naturally disadvantageous in view of the cost.
Furthermore, if a flat portion for mounting a fan is formed on the end of the shaft using a milling machine or the like, the cost increases in terms of machining, and in addition, there involves an inconvenience in that an axial dimension of the motor itself increases due to the presence of the flat portion.
The present invention has been achieved to overcome the above-described disadvantages and problems.
It is a first object of the present invention to provide an inexpensive flat motor device in which a rotor hub is directly resin molded on a shaft to thereby form a rotor portion, and a fan is directly mounted on the end surface of a rotor hub to make an axial dimension small, facilitate the producing operation and reduce the number of parts.
It is second object of the present invention to provide a producing method which in case of producing the aforesaid flat motor device, can positively carry out resin mold molding without use of a sleeve.
It is a third object of the present invention to provide a producing apparatus which can prevent resins from flowing into unnecessary portions during resin molding.